Deflection circuit



R. B. LE ROY DEFLECTION CIRCUIT 2 SHEETS-SHEET l Fil ed March 20, 194530 r ll 300 V. +450 V- TO COUNTER CENTERING VOLTAGE SOURCE SIGNAL BEINGCOUNTER FROM GWEEP CIRCUIT ADJUSTABLE STEP MARKER ,RAYMOND B. LEROY Dec.4, 1951 R. B. LE ROY 2,576,943

DEFLECTION CIRCUIT Filed March 20, 1945 2 SHEETS-SHEET 2 GRID VOLTAGE OFTUBE IO I I l l I l VOLTAGE AT (B) TERMINALZ? l I l l I GRID VOLTAGE OFTUBE l2 CUT-OFF POTENTIAL OUTPUT VOLTAGE AT 380 VOLTS V LTAGE 1 AT POINT"Y"APPL|ED TO UPPER DEFLECTION ll" PLATE OF +v C.R.TUBE

CENTERING VO LTA 6 E Jrwwwbom- RAYMOND B. LEROY Patented Dec. 4, 1951DEFLEC TION CIRCUIT Raymond-B. Le Roy, United States Navy ApplicationMarch 20, 1945, Serial No. 583,822

(Granted under the act of March 3, 188%, as amended: April 30, 1928; 3700.- G. 757) v 9 Claims.

This'invention relates to cathode ray' devices and is particularlyconcerned with a circuit for generating a voltage wave-form for use indefleeting the electron beam of a cathode ray tube to cause downwarddisplacement of the timing axis'at a predetermined point in thehorizontal sweep. One application of the invention is to provide'anadjustable step on the sweep trace of a cathode ray tube for accurateran e measurement purposes, e. g., in radio-echo ranging andobject-detecting apparatus.

It is an object of this'invention to provide improved step-generatingmeans for causing downward deflection of the electron beam of a cathoderay tube at selected points in the horizontal sweepof said tube.

Another object of the invention is to provide a step generator of thisclass which is simple in operation, compact, and which includes aminimum of necessary circuitcomponents.

A further object of the invention is the provision of a gas-filledgrid-controlled discharge tube circuit arrangement in which the firingof this tube can be adjusted within certain desired limits, and furtheremploying an auxiliary electron discharge device which is arranged insuch a manner as to extinguish the plat'e-current-fiow through thegas-filled discharge tube to allow its control grid'electrode toregaincontrol in readinessfor the next firing cycle ofits controlvoltage.

A'still further-object of the invention is topro-= vide an improvedrange step' generating circuit for generating an adjustable step markerwhich is movable along the timing sweep of a cathode ray tube to theposition of an echo indication whose range is desired; the position ofthe rangestep being capable of adjustment along'th weep trace over acomparatively wide range.

According to the invention, a circuit arrangement is provided containinga pair of electron discharge devices .with their anode elementsconnected in parallel'with one another and to one of? the: verticaldeflecting plates-of a cathode ray tube. the first electron dischargedevice being a gas-filled'tube of the type'including a" control grid,and-"the second. electron discharge device being a so-called hard tubeor high vacuum tube which may be, for example, a relatively lowimpedance triode. The circuit is arranged in such a manner that theoutput of the gasfilled'tubesupplies the adjustable off-set or step tothe sweep of the cathode ray tube-for producingthe desired downwarddisplacement of the: timing axis, and the output of the hard tube orsecond: electron discharge device is used to control the extinction ofthe gasfilled tube. The control voltages supplied to the control grid ofboth electron discharge devices are alternating non-sinusoidalpotentials of the same frequency and of the phase relationshiphereinafter disclosed. In the preferred embodiment exponential orsawtooth control voltages are supplied to the control grid of" thegas-filled tube and square-wave control voltages are fed to the controlgrid of the hard tube. It is de sirable that these control voltages befed to the respective control grids in such phase relationship that thepositive increment of the control potential supplied to the grid of thegas-filled tube will occur simultaneously with the arrival of thenegative increment'of the control potential fed to the grid of the hardtube whereby the latter is rendered conducting simultaneously with thearrival of the negative increment of the control potential at the gridof said gas-filled tube. The resistance of said hard tube during theconduction period is of such value as to present a low impedanceelectronic path the effect of which is to decrease the anode potentialof said gas-filled tube to a value below the minimum voltage necessaryto maintain said gasfilled tube conductive thereby to extinguish theplate current flow through the gas-filled tube and enable its grid toregain control in readiness for the next keying increment of the'controlpotential cyclically fed thereto. The sawtooth control voltage may bederived either from the same source of sweep voltage which is suppliedto the horizontal deflection plates of the cathode ray tube to provideits timing axis or it may be generated'independently and synchronizedwith the horizontal sweep of the cathode ray tube. The quiescentpotential of the hard tube is fixed by its circuit.

Other advantages and features of the inven tion will be apparent fromthe following particular description thereof made in connection with theaccompanying drawing, in which Fig. l is a circuit diagram showing thepreferred form of this invention;

Fig. 2 shows a set of explanatory curves to illustrate the operation ofthe circuit of Fig. 1, and

Fig. 3 is an end view of a cathode rayrange tube showing one form ofindication obtained on its screen by the practice of the presentinvention.

Referring now to Fig. l, the circuit includes a pair of electronic pathsor electron discharge tubes HI and It. The tube [0 is a gas-filledtriode having a cathode M- of the indirectly heated type, a control grid15 and a plate or anode Hi. The cathode I4 is positively biased inrelation to the grid l5 by means of a resistor I! in shunt with acapacitor l8. The resistor l1! and the capacitor 18 form an RC peakingcircuit to uphold the cathode bias during the interval that the platevoltage begins to decrease and the tube l0 commences to cutoff. Sawtoothcontrol voltages, of the wave-form shown in curve A of Fig. 2, aresupplied to the grid 55 of the tube In at the terminal 19 from asuitable source (not shown) which in one application of the device maybe the saw-tooth output from the plate of the sweep. generator tube (notshown) of the sweep generator unit for the cathode ray tube employed forrange determination in a radio-echo ranging and object-detectingapparatus.

Connected in parallel with the anode l6 of the gas-tube I0 is the plateor anode 20 of the tube l2, which is a low impedance triode having acathode 2! of the indirectly heated type and a control grid 22. Thecathode 2! is normally biased beyond cut-off by resistors 23 and 24which are of such values as to provide a bias slightly beyondplate-current cut-off for the tube [2 with low bleeder current. Theresistors 25 and 26 form a voltage-divider connecting the anodes i6 and20 to a source of high voltage (of the order of 450 volts), theseresistors having such values as to provide satisfactory plate currentthrough tube I0, and 380 volts on the plates l6 and 20 of the tubes I0and I2 res ectively when both tubes are non-conducting. The voltagesupply sources and the cathode heating supply are omitted forsimplifying the circuit.

Square wave control potentials, as depicted by the waveform of curve Bin Fig. 2, are fed to the grid 22 of the tube l2 at the terminal 21 froma suitable source (not shown) through the differentiating circuitcomposed of the capacitor 28 and the resistor 29. The resistor 29 andthe capacitor 28 are of such values as to allow saturation plate currentof the tube l2 for an interval of time long enough after completion ofthe sweep for the control grid voltage of the tube ill to drop belowcutoff. The wave-form of the differentiated signal applied to the grid22 of the tube I2 is shown in curve C" of Fig. 2. It is to be understoodthat the saw-tooth waves and the square-waves which control theoperation of the tubes I0 and I2 are supplied to the respective grids ofthese tubes in such phase and so synchronized as to have the phaserelationship substantially as shown by the curves A and"B respectivelyof Fig. 2.

In the plate circuit of tube [2 are the coupling capacitors 30 and 3i, aresistor 33, and the upper vertical deflection plate 34 of a cathode raytube 35. Curve D of Fig. 2 is a graphic representation of the wave-format point X of Fig. 1 and depicts the combined output from the plates I6and 20 of the tubes I0 and I2, respectively. The resistor 33 and thecapacitor 30 form a differentiating circuit for producing an exponentialdischarge curve on the trace of the cathode ray tube 35. The value ofthe capacitor 30 in conjunction with the resistor 33 determines thelength of the exponential discharge curve (range step at point Y andshown by curve E in Fig. 2). The capacitor 30 may be, if desired,replaced by a parallel arrangement of capacitors with a suitableswitching arrangement provided for selectively mally biased to beyondcutoff. When the grid voltage (algebraic difference of the cathodevoltage and the saw-tooth control voltage) reaches the critical point,tube l0 conducts, the grid l5 at this time losing control of the tube. Asteady plate-current flow through the tube [0 and the resistor 26 causesa steady potential at the plate N5 of the tube I0 which is lower by theIR drop across the resistor 26 than the potential at the beginning ofthe viewing cycle. This square waveform is applied to the upper verticaldeflection plate 34 of the cathode ray tube 35 through thedifferentiating circuit composed of the capacitor 30 and the resistor33, as above-mentioned, thereby producing an exponential discharge curveon the trace of the cathode ray tube.

It is necessary that some means must be provided to remove the platevoltage from the tube ID at the completion of the viewing cycle to allowthe grid [5 of tube H] to regain control and be ready for the nextfiring cycle. As above-described, this function is performed by the tubel2 which is normally biased beyond cutoff by the resistors 23 and 24.The grid 22 of tube I2 is coupled through the differentiating circuitcomposed of the capacitor 28 and the resistor 29 to the same source ofnegative souare wave voltage which blocks the sweep generator tube (notshown) emploved for the cathode ray tube 35. At the end of the part ofthe viewing cycle when sweep volta e is generated by the swee generatortube (not shown) and plate current is dra n by its plate, the grid [5 ofthe tube I0 is again very negative with respect to the cathode l4. Atthis instant, the following edge of the negative square wave ap lied tothe grid [5 of the tube I0 is s inging positive, and the t be l2conducts. Since the plates l6 and 20 of the tubes ID and I2 res ectivelyare connected together in parallel, the voltage on the plate 15 of thetube ID will decrease, this voltage decrease being more than s fiicientto extinguish plate current flow through the t be ID, allowing its gridl5 to re ain control. The arrangement of this circuit thus has theadvanta e that the tube I2 is driven into conduction only a fewmicroseconds to conserve power.

Control of the biasing potential of the cathode 14 may be obtained bvany desirable means such as, for example, by the voltage dividerarrangement formed by a known form of selective resistor networks 40 and4|, and the adjustable resistor 42. the movable slider 45 of theresistor 42 being preferably connected to the cathode lead 46 of thegas-filled tube l0. Suitable gearing 41 may be provided for operatingthe resistor slider 45, and range counter mechanism 48 may be includedfor range indication.

By controlling the bias the firing potential of the gas-filled tube l 0may be caused to take place either at points a, b or c on the sawtoothwave A shown in Fig. 2 whereby the tube I 0 can be fired at apredetermined selected potential and thus the position of the outputsweep displacement voltage or step along the timing axis may be adjustedas desired to produce downward displacement of the timing axis at themeasuring point of an echo indication whose range is desired.

It is to be understood that positive sawtooth sweep voltages are appliedto the right horizontal plate of the cathode ray tube 35 to produce thehorizontal time axis. Negative video signals or marker voltages areapplied to the lower vertical deflection plate of the cathode ray tube35, causing upward displacement of the sweep. The negative step markeror displacement,voltage-from.

displacement of the-timing axis of 'the'cathode raytube. Additionally,it is to be understood that positive square waves from-a source (notshown) are applied to the control electrode (not shown) of thecathoderay tube 35 and serve to --unblank the indicating tube during theviewing or receiving period, as is a common practice in art.

While Ihave shown and described above apreferred embodiment of myinvention, it is'to' be understood that various changes andmodifications may be made therein without departing from the spirit ofthe invention andthe scope of the appended. claims.

.The invention herein described may b'e-m'anufactured and used by or forthe Government of the UnitedStates of America for governmental purposeswithout. the payment of anyroyalties thereon or therefor.

WhatI claim is:

1. In combination, a pair of electron discharge devices each having ananode, a cathode and a control electrode, circuit means for connectingsaid anodesin parallel to a source of potentials and to an outputcircuit and for biasing. the oathodes so that said devices pass currentin response to positive potential signals applied to the controlelectrodes thereof, a first source of alternat ing non-sinusoidalcontrol voltages applied to the control electrode of one of saiddischarge devices for establishing anode-current flow duringpositiveexcursions thereof to initiate formation of a pulse signal in saidoutput circuit, means for varying the cathode bias of said one dischargedevice for determining the time current flow is established, a secondsource of alternating nonsinuscidal control volta es 'of the frequencyof said first source and 180 degrees out of phase therewith, andcoupling means applying said second source to the other controlelectrode for renderin said second discharge-devices conduct ingsubstantially at the beginning'o'f'the positive excursion of said secondcontrol voltage to'provide a low impedance ath to groundfor said onedischarge device to extinguish said'anode-curr'ent flowand'to'terminateformation of saidpulse signal.

2. In combination, a gaseous tube havingan anode, a cathode and acontrolelectrode with the cathode thereof biased so that ionization ocours inresponse to positive potential 'signa'ls'applied to saidcontrolelectrode; a high vacuum discharge device having ananode;a'cathode and a control electrode" with the cathode thereof biased .sothat the device passes current in response to application of positivepotential signals to the control electrode thereof, circuit meansconnecting the anode of said tube and the anode of saiddischarge devicein'parallelto a source of potential and to arr-output circuit;a'first'sou'rce of -said discharge device for rendering said dis? chargedevice conducting substantially at thebeginning of the positiveexcursions of said secondcontrol voltage to provide a low impedance pathto-ground. for said tube thereby extinguishing ionization thereof andterminating formation of;

said pulse signal.

- 3. Incombinationapair of electron discharge devices each having ananode, a cathode anda control electrode, circuit means for connectingsaid anodes in parallel to a source of potential and to an outputcircuit and for biasing the cathodessothat said devices pass current inresponse topositive potential signals applied to the control electrodes,a first source of alternating nonesinusoidal control voltages ofsaw-tooth waveform applied to the control electrode of one of saiddischarge devices for establishing anodecurrent iiow duringpositiveexcursions thereof to. initiate formation of apulsesignal in saidoutputcircuit, bias control means for the cathodeot said. one dischargedeviceoperable to determine the time. the anode-current flow isestablished, a second source of alternating non-sinusoidal controlvoltages of rectangular Waveform having aIfrequency of said first sourceand degrees outof phase therewith, and differentiating means applyingsaid second source to the other control electrode'for rendering saidsecond discharge device conducting substantially at the beginning of the.positiveexcursions of saidsecond control voltage to provide a lowimpedance path to groundfor said one discharge device therebyextinguishing. saidancde-current flow and. terminating formation of saidpulse signal.

4... In combination, a gaseous tube having an anode, a cathode and acontrol electrode with the-cathode biased so that ionization occurs inresponse to positive potential signals applied to saidicontrolelectrode,a high vacuum discharge device having an anode, a cathode and a controlelectrode withthe cathode thereof biased so that the. device passescurrent in response to application of positive potential signals to thecontrol electrode thereof, circuit means connect ing the anode of saidtube and the anode of said discharge deviceinparallel to asource ofpotential and to an output circuit, a first source of alternatingnon-sinusoidal control voltages applied to the control electrode of saidtube to'ionize said tube durin positive excursions thereof forinitiating formation of a pulse signal in said output circuit, asecond-source of alternating nonsinusoidal control voltages of thefrequency of said firstsource and 180 degrees out of phase therewith,coupling means applying said second source to the control electrode ofsaid discharge device for rendering said discharge device conductingsubstantially at the beginning of positive excursions of said secondcontrolvoltage to provide a low impedance path to ground for said tubethereby extinguishing ionization of the gas and terminating formationof:-said .pulse signal,

andmeans connected in the cathode circuit of" said 'tubeioperative tohold the biason the oathode of said tube during the period immediatelypreceding extinction-of ionization to insure substantially sharpdeionization of said tube.

5. In combination, a pair of electron dischargedevices each having ananode, a cathode and a control electrode, circuit means forconnectingsaid-anodesin parallel. to a source ofpotential;

andtoan output circuit and for biasing the cath odes solthat saiddevices pass current in; response tonpositivepotential signals appliedto the control electrodes, a first source of alternating nonsinusoidalcontrol voltages of saw-tooth waveform applied to the control electrodeof one of said discharge devices for establishing anodecurrent flowduring positive excursions thereof to initiate formation of a pulsesignal in said output circuit, a second source of alternatingnonsinusoidal control voltages of rectangular wavee form and of afrequency corresponding to the frequency of said first source and 180degrees out of phase therewith, difierentiating means applying saidsecond source to the other control electrode for rendering said seconddischarge device conducting substantially at the beginning of positiveexcursions of said second control voltage to provide a low impedancepath to ground for said one discharge device thereby extinguishing saidanode-current flow and terminating formation of said pulse signal, andmeans operative to selectively establish the cathode bias of said firstdischarge device for initiating formation of the output pulse at anypredetermined point on the positively increasing portion of thesaw-tooth waveform.

6. In combination, a gas-filled tube having an anode, a cathode and agrid; a high vacuum tube of relatively low impedance having an anode, acathode and a grid, the anodes of both of said tubes being connected inparallel; a cathode ray tube having horizontal and vertical deflectionplates, and means for controlling said gas tube for producing astep-forming voltage which is applied to one of said deflection plates;the lastnamed means including means comprising alternatingnon-sinusoidal control voltages of different wave-forms applied to therespective grids of both tubes, said control voltages being supplied insuch phase relationship so that the positive increment of the controlpotential fed to the grid of said gas-filled tube occurs simultaneouslywith the arrival of the negative increment of the control potential fedto the grid of said high vacuum tube whereby conduction thereof occurssimultaneously with the arrival of the negative increment of the controlpotential at the grid of the gas-filled tube, the resistance of saidhigh vacuum tube during its conduction period being of such value as topresent a low impedance electronic path effective to decrease the anodepotential of said gas-filled tube to a value below the minimum voltagenecessary to maintain said gas filled tube conductive thereby toextinguish platecurrent flow through the latter and enable its grid toregain control in readiness for the next control potential cylically fedthereto; and means operative to provide an adjustable bias on thecathode of said gas-filled tube for varying the point at which firingthereof occurs thereby to enable the position of said step-formingvoltage output from said gas-filled tube to be varied as desired alongthe timing axis of said cathode ray tube.

v '7. In an indicating system, a cathode ray tube having a pair ofdeflecting means, a sweep circuit operative in accordance with controlvoltages of rectangular waveform tofeed sweep potentials of saw-toothwaveform having the frequency of said control voltages and 180 degreesout of phase therewith to one pair ofsaid deflecting means, a pair ofelectron discharge devices each having an anode, a cathode and a controlelectrode, circuit means for connecting said'anodes in parallel toasource of potential and to the other pair of said deflecting means andfor biasing said oath-3' odes'so that said devices pass current inresponse to positive potentials applied to said control elec-' trodes,means applying said sweep potentials to one of said eontrol electrodesto render one of said devices conducting at a particular voltage pointof said saw-tooth waveforms determined by the cathode bias of said onedevice, and a differentiating circuit for applying said control voltagesof rectangular waveform to the other control electrode for rendering theother discharge device conducting at the beginning of positiveexcursions of said rectangular waveforms to provide a low impedance pathto ground for said one discharge device to thereby extinguish conductionthereof.

8. In an indicating system, a cathode ray tube having a pair ofdeflecting means, a sweep circuit operative in accordance with controlvoltages of rectangular waveform to feed sweep potentials of saw-toothwaveform having a frequency corresponding to the frequency of saidcontrol voltages and degrees out of phase therewith to one pair of saiddeflecting means, a pair of electron discharge devices each having ananode, a cathode and a control electrode, circuit means for connectingsaid anodes in parallel to the other pair of said deflecting means andfor biasing said cathodes so that said devices pass current in responseto positive potentials applied to said control electrodes, couplingmeans applying said sweep potentials to one of said control electrodesto render one of said devices conducting at a particular voltage pointof said saw-tooth waveforms determined by the cathode bias of said onedevice, a differentiating circuit for applying said control voltages tothe other control electrode for rendering the other discharge deviceconducting at the beginning of positive excursion of said rectangularwaveforms to provide a low impedance path to ground for said onedischarge device to thereby extinguish conduction thereof, and meansoperable to selectively vary the oath-- ode bias on said one dischargedevice for establishing conduction thereof at predetermined voltagepoints on the saw-tooth waveforms.

9. In an indicating system, a cathode ray tube having two pairs ofdeflection plates, a control voltage of rectangular waveform, saw-toothsweep circuit operative responsively to said control voltage ofrectangular waveform and connected to one pair of said deflectionplates, a gaseous discharge tube having an anode, a cathode-and acontrol electrode with the cathode so biased that ionization occurs inres onse to positive potential signals applied to said control elec-'trode, a hi h vacuum discharge tube having an anode, a cathode and acontrol electrode with the cathode thereof biased so that the tubepasses current in response to the application of positive potentialsignals to the control electrode thereof, the anode ofsaid gaseous tubebeing connected to the anode of said vacuum tube, resistance meansconnecting said anodes to a source of potential, a differentiatingcircuit connecting said anodes'to a plate of the other pair of saiddeflecting plates, means connecting said sweep circuit to the controlelectrode of said gaseous tube to render said tube conducting at aparticular voltage point of the saw-tooth waveform determined by thecathode bias of said vacuum tube, and coupling means applying saidcontrol voltage of rectangular waveform to the control electrode of saidvacuum tube for rendering said vacuum tube conducting at the beginningof positive excurlsions of said rectangular waveform to provide a lowimpedance path to ground for said gaseous Number tube to therebyextinguish conduction thereof. 2,286,894 RAYMOND B. LE ROY. 2,301,1962,350,069 REFERENCES CITED 5 23503333 The following references are ofrecord in the 2,412,210 file of this patent: 2,428,149

UNITED STATES PATENTS Number Name Date 10 2,147,472 Ulrey Feb. 14, 19392,280,949 Hall Apr. 28, 1942 10 Name Date Browne et a1 June 16, 1942Bradford Nov. 10, 1942 Schrader et a1. May 30, 1944 Hall June 6, 1944Edson et a1 Dec. 10, 1946 Falk Sept. 30, 1947 OTHER REFERENCESElectronics, January 1942, Des. 34, 35, Photofiash Synchronizer Tester,by Marsal.

